The present disclosure relates to a vehicle torsion beam suspension and a vehicle torsion beam.
Japanese Unexamined Patent Publication Nos. 2013-091433 and 2016-199209 describe torsion beam suspensions that are a type of vehicle suspension. These suspensions include left and right trailing arms relative to a vehicle body each supporting a wheel and a torsion beam that connects these arms. The trailing arms are rotatably joined to the vehicle body at their base ends and wheels are rotatably mounted to the leading ends. The opposite ends of the torsion beam are bonded to the trailing arms. Spring seats are bonded to the ends of the torsion beam and the trailing arms, and coil springs are disposed between the spring seats and the vehicle body.
Torsion beams are required to have a suitable torsion stiffness for position control during a body roll of the vehicle. Since torsion beams are bonded to the trailing arms and the spring seats at the opposite ends, the torsion beams are also required to have a sufficient bond strength. The suspensions described in Japanese Unexamined Patent Publication Nos. 2013-091433 and 2016-199209 each include a torsion beam having a closed cross section. This torsion beam includes a beam center portion having an inverse substantially v-shaped cross section defined by an upper wall and a lower wall both protruding upward. This sectional shape gives the torsion beam a lower degree of torsional resistance. The sectional shape of the beam varies from the beam center portion toward the opposite ends of the beam such that a space between the upper wall and the lower wall is gradually increased, that is, the cross-sectional area is gradually increased. This structure increases the bending strength of the beam.
As discussed above, the torsion beam is required to have both suitable torsional stiffness and sufficient bending strength. The conventional torsion beam is typically formed from a steel pipe having a constant circumferential length throughout the pipe length by, for example, pressing. Since the circumferential length of the torsion beam is constant, it is difficult to fully satisfy the requirements by only changing the sectional shape.